The overall purpose of this study is to determine the role of oral and systemic bone mineral density (BMD) in the development of new and progressive periodontal disease in postmenopausal women. We hypothesize that low BMD will be associated with both new and progressive periodontitis over time by increasing susceptibility to destructive periodontitis. We propose a longitudinal assessment of BMD and its role in establishment of periodontal disease in postmenopausal women with systematic studies using sensitive and accurate measures of skeletal and oral BMD, and periodontal disease. As part of the BMD assessment, we will further validate the methodology for oral BMD. In concert with these, assessment of a variety of potential co-risk factors for both low BMD and periodontitis will allow us to determine their contribution to this association. The systemic covariates include age, body mass index, smoking, alcohol, hormone use, socioeconomic and psychosocial factors, medications, medical and reproductive history, and diet. Local covariates include plaque, gingivitis, probing depth, previous dental care, and dental care habits. Study subjects will be recruited from an established cohort of postmenopausal women with baseline assessments of BMD and periodontitis as part of an ongoing cross-sectional study. We propose a 3-vear follow-up examination in 1000 postmenopausal women already enrolled in the NIH Women's Health Initiative study. To date, studies have not characterized the specific role of BMD either skeletal or mandibular on periodontal disease incidence and progression in a large cohort of postmenopausal women. Our preliminary cross-sectional studies have determined that skeletal BMD is associated with alveolar crestal height, tooth loss and clinical attachment loss. The proposed longitudinal study will have sufficient sample size and statistical power to assess the temporal relationship between BMD and periodontitis and the effects of a large set of co-risk factors and potential confounding factors affecting osteopenia, periodontal disease or both. This study provides a unique opportunity to define this relationship in a cost effective manner in a cohort of postmenopausal women under study as part of the Women's Health Initiative and has great practical significance. Low BMD is likely of considerable importance in the onset and progression of periodontitis. Hence once the relationship is established, modalities effective in the prevention and treatment of osteoporosis may prove useful for prevention and treatment of periodontitis and subsequent tooth loss.